High pressure presses have been used for decades in the manufacture of synthetic diamond. Such presses are capable of exerting a high pressure and high temperature on a volume of carbonaceous material to create conditions for sintering polycrystalline diamond. Known designs for high pressure presses include, but are not limited to, the belt press, the tetrahedral press, and the cubic press.
FIG. 1 shows a basic design for a conventional cubic press 10 known in the art.
The design generally includes six press bases 12, with each press base 12 facing towards a common central point 14. The press bases 12 have a generally conical shape, with an outer surface 16 and an inner surface 18. The inner surface 18 houses a piston 20, which is capable of being displaced towards the central point 14.
FIG. 2 shows a close-up view of components surrounding the central point 14 of the cubic press 10. Guide pins 22 help to keep the pistons 20 aligned as they move in and out. Tooling 24 is coupled to each of pistons 20 and may include a square-shaped surface 26 aligned perpendicularly to the axis of motion of the piston 20. The square-shaped surfaces 26 of the tooling 24 converge upon a defined cube-shaped volume. This volume may be occupied with a cube-shaped reaction cell upon which the square shaped surfaces 26 apply pressure and heat to create the conditions necessary to form synthetic diamond.
In ideal operation, the cubic press 10 operates by applying force in equal amounts and directions to all six sides of the cubic volume. However, even relatively minor imbalances in the amount or direction of force applied to any one side of the cubic volume can lead to the cubic press not operating properly and may damage components of the cubic press.
Referring back to FIG. 1, one known design of a cubic press 10 is shown. The press includes a plurality of tie bars 28 that may generally comprise large diameter bolts having a capped end and a threaded end. For example, in one embodiment, the bolts may exhibit a diameter of approximately nine (9) inches. The tie bars 28 are positioned so as to extend between each pair of adjacent press bases 12. Pockets are formed through the press bases 12 for receiving the tie bars 28. The threaded end of a tie bar 28 is passed through a pocket in a first press base and a pocket in a second press base adjacent to the first press base such that the capped end abuts or is flush with a surface of the first press base. A nut is screwed on the threaded end of the tie bar 28 and tightened against the second press base thereby placing the tie bar 28 in tension between pairs of adjacent press bases 12. The cumulative effect of tie bars 28 being positioned between each pair of adjacent press bases is the formation of a tie bar frame that attempts to provide stability to the cubic press 10 and help counteract any unequal distribution of force and the associated stress this may otherwise place on the high pressure press.
As also shown in FIG. 1, conventional cubic presses may include a spacer 30 positioned between each pair of adjacent press bases 12. The spacer 30 may be configured as a quarter section of a hollow tube and may be used to help position the press bases 12 in the desired cubic configuration. That is to say, the spacers 30 may have a length approximately equal to the distance that the press bases 12 should be spaced apart from one another. While the tie bars 28 are placed in a tensile stress condition, the spacers 30 are placed under compression between pairs of adjacent press bases 12. It is noted that the spacers 30 also have a much smaller cross sectional area as compared to the cross sectional area of the tie bars 28 (as taken in a direction substantially perpendicular to their respective lengths). Additionally, the spacers 30 conventionally act to position the bases with respect to each other only when the press 10 is in a pressurized condition. This type of loading cycle is also detrimental to the fatigue life of the spacers and associated components.
However, due to design weaknesses in, for example, load cycling and alignment of the press bases 12, tie bars 28 and spacers 30 of the above-described configuration, high cyclical bending stresses are often induced, for example, in the threads of the tie bars 28 and the hydraulic cavities of the press bases 12 leading to a significant reduction in the fatigue life of the cubic press components.
For example, the press bases in the above-described configuration may be more likely to fail after fewer cycles due to, for example, the machining out large diameter pockets in the press bases for receipt of the large diameter tie bars (i.e., the removal of a substantial amount of material from the press bases).
Further, with respect to alignment of the components of the cubic press, the above described configuration provides no means for helping to ensure proper alignment of the components.
In addition to potential issues pertaining to alignment and fatigue, the above configuration is also difficult to manufacture and assemble.
With respect to the manufacture of the above described cubic press, the components of the cubic press are each difficult and costly to produce. For example, the process of machining out large quantities of material from a press base to form a pocket for receiving a large diameter bolt, including achieving desired tolerances in such components, is an expensive and difficult manufacturing task.
Furthermore, manufacture and assembly of the above-described cubic press is often difficult and lacking in accuracy. For example, alignment and installation of the large diameter bolt within the pockets of the associated bases is a difficult and time consuming task. Likewise, applying the necessary and desired torque to tighten the large nut on a large diameter screw is a labor intensive, potentially dangerous, and inaccurate process.
Thus, it would be advantageous to provide an improved high pressure press configuration design and method of making the same.